1. Field of the Invention
The resent invention relates to a copy lens for copy machines and processing equipments suitable for reproducing images as large as originals, and, more particularly, to a copy lens comprising four lens elements arranged in symmetrical with an aperture of the copy lens.
2. Description of Related Art
Much attention has given to various optical approaches relating to compact and low cost copy machines which include four element copy lenses. In most copy lenses lens elements are arranged symmetrically with an aperture to reduce the number of lens elements for satisfying demands in the field of copy equipment industry toward compactness and cheapness. The symmetrical arrangement of four element copy lenses enables these lenses to be assembled through a reduced number of processes and, consequently yield manufacturing cost saving in addition to a great reduction in aggravation of optical characteristics, such as distortion.
Examples of such four element copy lenses are described in, for instance, Japanese Unexamined Patent Publications Nos. 55-81316, 57-161823, 58- 9118 and 61- 292119. In particular, the copy lens described in Japanese Unexamined Patent Publications No. 61- 292119 has proven to be an excellent copy lens and is compact and well corrected on various aberrations.
While the copy lenses as described in the above-mentioned publications may have advantages over prior art, nevertheless, a more economical constraint must be imposed upon the material, processability and price of each lens element which are always user's demands.